A method for the continuous production of alkyl xanthates

Abstract

The application relates to a method for continuously producing alkyl xanthate, belonging to the field of alkyl xanthate production, and comprising the following steps: step one: adding cyclohexane and organic alcohol into a solid-liquid mixer in proportion; step two: adding solid alkali into the solid-liquid mixer and crushing and stirring by using an emulsifying machine; step three: continuously adding carbon disulfide into a dynamic tubular reactor by using a precision metering plunger pump, and after the reaction is completed, the slurry is discharged from a dynamic tubular reactor discharge port into a slurry storage tank; and step four: the slurry is sequentially transported to a vacuum spray drying system by using a screw pump, and after drying, alkyl xanthate is obtained. The application uses a dynamic tubular reactor to synthesize alkyl xanthate, the solid alkali is easy to ionize, and after ionization, the solid alkali collides with organic alcohol, carbon disulfide and an organic solvent to react, and the nucleophilic reaction rate is accelerated.

Description

Technical Field

[0001] This invention belongs to the field of alkyl xanthate production, specifically a method for the continuous production of alkyl xanthates using a composite phase transfer catalyst. Background Technology

[0002] Alkyl xanthates are collectors with strong collecting power but weak selectivity, widely used in the flotation of copper, zinc, nickel, and gold-bearing ferrous ore, with a large market demand. Currently, industrial production methods include kneading and solvent methods. Kneading generates significant dust and produces low-quality products. Solvent methods for synthesizing alkyl xanthates involve large amounts of organic solvents or reactants, making it difficult for them to fully contact and react. As alkyl xanthates are gradually formed, they readily encapsulate unreacted solid bases, preventing further reaction and resulting in low product content, high impurities, long reaction times, and low efficiency. Even in the later stages of alkyl xanthate synthesis, as the reaction system thickens, the produced alkyl xanthates continue to encapsulate unreacted bases. Increasing the solvent dosage can alleviate the encapsulation problem but reduces production efficiency and increases the cost of solvent recovery. Summary of the Invention

[0003] This invention provides a method for the continuous production of alkyl xanthates using a composite phase transfer catalyst, thereby overcoming the deficiencies in the prior art.

[0004] This invention is achieved through the following technical solution: A method for continuous production of alkyl xanthates includes the following steps: Step 1: Add cyclohexane and organic alcohol to the solid-liquid mixer in the specified proportions; Step 2: Solid alkali is added to a solid-liquid mixer and crushed and stirred using an emulsifier. After being mixed evenly, the feed flow rate is controlled by a precise metering device and continuously fed into a dynamic tube reactor. Step 3: Carbon disulfide is continuously added to the dynamic tubular reactor using a precision metering plunger pump. After the reaction is completed, the slurry enters the slurry storage tank from the outlet of the dynamic tubular reactor. Step 4: The slurry is pumped to a vacuum spray drying system by a screw pump and dried to obtain alkyl xanthate.

[0005] In the continuous production method of alkyl xanthates described above, the solid base is sodium hydroxide or potassium hydroxide, wherein the sodium hydroxide content is ≥96% and the potassium hydroxide content is ≥90%.

[0006] In the continuous production method of alkyl xanthates described above, the molar ratio of cyclohexane, organic alcohol, carbon disulfide, and solid alkali is 2-10:1-1.05:0.95-1.1:1-1.1.

[0007] The method for continuous production of alkyl xanthates as described above, wherein the organic alcohol is any one or a mixture of any two or more of the following in any proportion: fatty alcohol, ethanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-octanol, and isooctanol.

[0008] In the continuous production method of alkyl xanthates described above, the synthesis residence time in the dynamic tube reactor is 5-50 min, the temperature in zone one is 20-28℃, the temperature in zone two is 28-40℃, and the liquid holdup is 1-10 L.

[0009] In the continuous production method of alkyl xanthates described above, the feed rate and residence time of the dynamic tube reactor are controlled by a feed pump.

[0010] The method for continuous production of alkyl xanthates as described above includes a vacuum spray drying system comprising a raw material tank, a heating chamber, a separation chamber, a discharge tank, a condenser, and a water replenisher. The raw material tank is preheated to a temperature of 75-90°C, and the temperature of the heating chamber is raised to 110-140°C (high-temperature nitrogen can be added during this process). The material enters the separation chamber together for solvent removal and drying. The dried product enters the product discharge tank via a screw conveyor, and the solvent is separated after condensation.

[0011] The advantages of this invention are: This invention uses a dynamic tubular reactor to catalyze the synthesis of alkyl xanthates. The solid base is easily ionized, and after ionization, it reacts with organic alcohols, carbon disulfide, and organic solvents, accelerating the nucleophilic reaction rate. This solves the problems in solvent-based synthesis of alkyl xanthates, such as excessive free base in the dried alkyl xanthates and low product yield due to the collector encapsulating the caustic base in the reaction process, which prevents the reaction from proceeding. The present invention uses a dynamic tubular reactor for continuous synthesis, which allows for good reaction control, low online material quantity, short reaction time, high efficiency, and higher safety than traditional batch reactors. The dynamic tubular reactor is equipped with dynamic stirring components, which ensure uniform mixing of reactants and stable product quality. Compared with batch reactors, the entire synthesis process is easier to clean, generates less waste, has a smaller footprint, high capacity, and can be scaled up proportionally by simply adding equipment without adjusting the material ratio. This invention uses vacuum spray drying technology to convert xanthate products into powder in one step, eliminating the need for further crushing, granulation, and sieving processes. The process is simple, and vacuum spray drying achieves fully automated continuous closed-loop operation of the entire process, from material feeding, atomization, drying, and powder collection. The entire process is sealed and there is no manual contact with the material. Moreover, the drying process parameters are easy to control, and the closed-loop operation with nitrogen gas during drying ensures high safety. The drying process is continuous, and the defect rate is significantly reduced compared to traditional drying methods. This invention employs a dynamic tubular reactor combined with a vacuum spray dryer, resulting in a small online liquid volume and high safety throughout the alkyl xanthate production process. The production process is continuous, controllable, and highly efficient, achieving safe, clean, efficient, energy-saving, and sustainable clean production of alkyl xanthates. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the synthesis operation in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the synthetic slurry in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the vacuum spray drying system of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the working interface of the vacuum spray drying system according to Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of powdered xanthate exiting through the sight glass during the vacuum spray drying process of Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the dried sodium isobutyl xanthate product of Example 1 of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] A method for continuous production of alkyl xanthates includes the following steps: Step 1: Add cyclohexane and organic alcohol to the solid-liquid mixer in the specified proportions; Step 2: Solid alkali is added to a solid-liquid mixer and crushed and stirred using an emulsifier. After being mixed evenly, the feed flow rate is controlled by a precise metering device and continuously fed into a dynamic tube reactor. Step 3: Carbon disulfide is continuously added to the dynamic tubular reactor using a precision metering plunger pump. After the reaction is completed, the slurry enters the slurry storage tank from the outlet of the dynamic tubular reactor. Step 4: The slurry is pumped to a vacuum spray drying system by a screw pump and dried to obtain alkyl xanthate.

[0016] Preferably, the solid alkali described in this embodiment is sodium hydroxide or potassium hydroxide, wherein the sodium hydroxide content is ≥96% and the potassium hydroxide content is ≥90%.

[0017] Preferably, in this embodiment, the molar ratio of cyclohexane, organic alcohol, carbon disulfide, and solid alkali is 2-10:1-1.05:0.95-1.1:1-1.1.

[0018] Preferably, the organic alcohol described in this embodiment is any one or a mixture of any two or more of the following in any proportion: fatty alcohol, ethanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-octanol, and isooctanol.

[0019] Preferably, in the dynamic tube reactor described in this embodiment, the synthesis residence time is 5-50 min, the temperature in zone one is 20-28℃, the temperature in zone two is 28-40℃, and the liquid holdup is 1-10 L.

[0020] Preferably, in this embodiment, the feed rate and residence time of the dynamic tubular reactor are controlled by a feed pump.

[0021] Preferably, the vacuum spray drying system described in this embodiment includes a raw material tank, a heating chamber, a separation chamber, a discharge tank, a condenser, and a water replenisher; the raw material tank is preheated to a temperature of 75-90°C, and the temperature of the heating chamber is raised to 110-140°C (high-temperature nitrogen can be added during this period), and the raw materials enter the separation chamber together for solvent removal and drying. The dried product enters the product discharge tank via a screw conveyor, and the solvent is separated after condensation.

[0022] Preferably, the dynamic reactor with a cooling medium temperature of -10℃ to 10℃ in this embodiment is a single tube or multiple tubes connected in parallel.

[0023] Preferably, the stirring blades inside the dynamic tube reactor described in this embodiment have a spiral propulsion structure, which makes the material flow approach a horizontal flow, avoids back mixing, and realizes continuous feeding and discharging.

[0024] Preferably, the dynamic tube reactor described in this embodiment includes a jacket, a reaction chamber, a stirring shaft, and a motor drive device. A cooling medium is introduced into the jacket, and the temperature of the cooling medium is -10℃ to 10℃.

[0025] Preferably, in this embodiment, the three materials—cyclohexane, organic alcohol, and solid alkali—are mixed and emulsified in a solid-liquid mixer using an emulsifier.

[0026] Preferably, the emulsifier described in this embodiment is equipped with a flow-increasing impeller, and the high shear strength causes the droplets encapsulating solids to collide and break, thereby achieving homogenization.

[0027] Preferably, in this embodiment, the slurry is kept at a constant temperature in the slurry storage tank for 15-25 minutes to allow any possible residual raw materials to react completely, thereby improving the purity of the finished product; the xanthium crystals grow uniformly, and the slurry state is stable; the buffering of the stored material ensures the stability of the feed in the subsequent drying section; the slurry storage tank is equipped with a jacket and cooling water to maintain the material temperature at 25-35°C; and a stirring device is installed at the bottom of the slurry storage tank to continuously stir and prevent the bottom of the material from crystallizing and clogging, which would cause poor material flow.

[0028] Example 1

[0029] like Figures 1-5 As shown, the specific process of this embodiment is as follows: (1) Mixing Add 4616.79g of cyclohexane and 1572.24g of isobutanol (99% purity) to a solid-liquid mixing container; (2) Emulsification and fragmentation Turn on the emulsifier, introduce nitrogen gas into the solid-liquid mixing container for protection, and add 837.5g of flake sodium hydroxide (96% purity) for emulsification and crushing; the temperature rises rapidly during the crushing process, so cooling water is introduced to cool it down.

[0030] (3) Synthesis Cyclohexane was introduced to clean the dynamic tube reactor. After thorough cleaning, the temperature of the mixture in (2) was reduced to below 28°C. The mixture was then pumped into the dynamic tube reactor using a peristaltic pump (holding capacity 10L). The peristaltic pump feed rate was set to 400mL / min. Carbon disulfide was pumped into the dynamic tube reactor using a precision metering plunger pump. The precision metering plunger pump feed rate was set to 66.30mL / min. The peristaltic pump and the precision metering plunger pump were turned on and off simultaneously. The residence time of the material in the dynamic tube reactor was 25min. The temperature of zone one of the dynamic tube reactor was 28°C, and the temperature of zone two was 32°C. The jacket of the dynamic tube reactor was circulated with a condensing medium to cool it down.

[0031] (4) Drying The material from the discharge end in (3) is pumped into the vacuum spray drying system. The temperature of the raw material tank of the dryer is 85℃, the temperature of the separation chamber is set at 125℃, and the vacuum degree is 0.072MPa. The material is controlled to be discharged within 60 minutes. After all the slurry is dried, 3479.9g of dried product is obtained (e.g., ...). Figure 6 (As shown).

[0032] The content of sodium isobutylxanthate in the dried product obtained in Example 2 was determined according to the standard YS / T 271.1-1994 Xanthate Chemical Analysis Method - Lead Acetate Titration Method. The effective content in the dried product was 94.13%, the mass content of free alkali was 0.056%, and the calculated yield was 94.7%.

[0033] Synthesis of sodium isobutylxanate from cyclohexane solvent: Weigh 1000g of recovered cyclohexane solvent and 297.1g of isobutanol (content 99%) and add them to a solid-liquid mixing container. Turn on the emulsifier and slowly add 163.64g of flake sodium hydroxide (content 96%) to emulsify and break down the emulsion. During this process, cooling water is passed through to lower the temperature until it drops below 28℃. The mixture was pumped into the dynamic tube reactor (holding capacity 2L) using a peristaltic pump, with the peristaltic pump feed rate set at 111.11 ml / min. Carbon disulfide was pumped into the dynamic tube reactor using a precision metering plunger pump, with the precision metering plunger pump feed rate set at 16.59 mL / min. The peristaltic pump and the precision metering plunger pump were turned on and off simultaneously. The residence time of the material in the dynamic tube reactor was 18 min. The temperature in zone one of the dynamic tube reactor was 28℃, and the temperature in zone two was 32℃. The jacket of the dynamic tube reactor was circulated with a condensing medium for cooling.

[0034] After the slurry at the discharge end of the dynamic tube reactor was dried, the content of sodium isobutyl xanthate was determined according to the standard YS / T 271.1-1994 Xanthate Chemical Analysis Method - Lead Acetate Titration Method. The effective content in the dried product was 93.67%, and the mass content of free alkali was 0.036%.

[0035] Example 2:

[0036] The difference from Example 1 is that the organic alcohol added is isopropanol, with 1335.95g of isopropanol (content 99%) added, 909g of flake sodium hydroxide (content 96%) emulsified and crushed, and 5540.148g of cyclohexane added. The residence time of the dynamic tubular reactor (holding capacity 2L) was controlled at 18min, and the feed rate of the peristaltic pump was set at 111.77mL / min. Carbon disulfide was injected into the dynamic tubular reactor through a precision metering plunger pump with a feed rate of 17.63mL / min. All other operations were the same.

[0037] According to the test, the sodium isopropyl xanthate obtained in Example 2 had an effective content of 96.32% and a free alkali content of 0.078% in the dried product, determined by the standard YS / T 271.1-1994 Xanthate Chemical Analysis Method - Lead Acetate Titration Method.

[0038] Sodium isopropyl xanthate synthesized from cyclohexane solvent Weigh 2500g of recovered cyclohexane solvent and 501.04g of isopropanol (content is 99%) and add them to a solid-liquid mixing container. Turn on the emulsifier and slowly add 340.91g of flake sodium hydroxide (content is 96%) to emulsify and break it up. During this process, cooling water is passed through to cool down the temperature until it drops below 28℃. The mixture was pumped into the dynamic tube reactor (2L) using a peristaltic pump at a feed rate of 100 mL / min. Carbon disulfide was pumped into the dynamic tube reactor (2L) using a precision metering plunger pump at a feed rate of 13.76 mL / min. The peristaltic pump and the precision metering plunger pump were turned on and off simultaneously. The residence time of the material in the dynamic tube reactor was 20 min. The temperature in zone one of the dynamic tube reactor was 25°C, and the temperature in zone two was 32°C. The jacket of the dynamic tube reactor was circulated with a cooling medium to lower the temperature.

[0039] After drying, the slurry at the discharge end of the dynamic tube reactor was tested. According to the standard YS / T 271.1-1994 Xanthate Chemical Analysis Method - Lead Acetate Titration Method, the effective content of xanthate in the dried product was 96.11%, and the mass content of free alkali was 0.049%.

[0040] Example 3:

[0041] Weigh 1035g of the recovered cyclohexane solvent and 165.63g of isobutanol (content 99%) and add them to a solid-liquid mixing container. Turn on the emulsifier and slowly add 129g of flake potassium hydroxide (content 96%) to emulsify and break it up. During this process, cooling water is passed through to cool down the temperature until it drops below 28℃. The mixture was pumped into the dynamic tube reactor (holding capacity 2L) using a peristaltic pump, with the peristaltic pump feed rate set at 80ml / min. Carbon disulfide was pumped into the dynamic tube reactor using a precision metering plunger pump, with the precision metering plunger pump feed rate set at 7.61mL / min. The peristaltic pump and the precision metering plunger pump were turned on and off simultaneously. The residence time of the material in the dynamic tube reactor was 25min. The temperature in zone one of the dynamic tube reactor was 27℃, and the temperature in zone two was 34℃. The jacket of the dynamic tube reactor was circulated with a condensing medium to cool it down.

[0042] After the slurry at the discharge end of the dynamic tube reactor was dried, the content of potassium isobutylxanthate was determined according to the standard YS / T 271.1-1994 Xanthate Chemical Analysis Method - Lead Acetate Titration Method. The effective content in the dried product was 95.47%, and the mass content of free alkali was 0.041%.

[0043] Comparative Example 1 A 30L glass reactor was used as the synthesis equipment. 15.228 kg of carbon disulfide was added as a solvent and raw material, followed by 1.730 kg of sodium hydroxide (96% purity) and 2.931 kg of isopropanol (99% purity). The rate of alcohol addition was controlled, and the reaction temperature was maintained at 32℃ for 6 hours. After the synthesis was completed, the mixture was dried using a spray drying system. The temperature of the raw material tank in the dryer was 45℃, the temperature of the separation chamber was set at 125℃, and the vacuum degree was 0.072 MPa. The time from material entry to discharge was controlled to be 60 minutes.

[0044] The sodium isopropyl xanthate obtained in the comparative sample was tested and its xanthate content was determined according to the standard YS / T 271.1-1994 Xanthate Chemical Analysis Method - Lead Acetate Titration Method. The effective content in the dried product was 88.76%, and the mass content of free alkali was 0.034%.

[0045] Comparative Example 2: A 1L three-necked flask was used as the synthesis apparatus. 418.77 kg of carbon disulfide was added as solvent and raw material, followed by 165.46 kg of potassium hydroxide (96% purity) and 92.42 kg of isobutanol (99% purity). The rate of alcohol addition was controlled, and the reaction temperature was maintained at 32℃ for 4 hours. A large amount of potassium hydroxide remained unreacted. A portion of the slurry was taken out, and it was clearly visible that the generated xanthate coated the unreacted potassium hydroxide, hindering its reaction. The synthesis continued for another 5 hours. After completion, the product was dried using a rotary evaporator at 110℃, a vacuum of 0.09 MPa, and a drying time of 2.5 hours. The xanthate content was determined according to standard YS / T 271.1-1994, Xanthate Chemical Analysis Method - Lead Acetate Titration Method. The effective content of the dried isobutyl xanthate was 86%, and the free alkali content was 2.5%. The product grade was low, with a significant excess of free alkali.

[0046] In summary, under the same drying conditions, the synthesis of alkyl xanthates using a dynamic tubular reactor in Examples 1-3 of this invention significantly improved the reaction rate compared to the traditional solvent synthesis process used in Comparative Examples 1-2. The reaction time was greatly shortened, the reaction rate was increased, and continuous discharge could be achieved, resulting in a significant improvement in production efficiency. The amount of solvent used online during the production process was also reduced, and safety was greatly improved.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for continuous production of alkyl xanthates, characterized in that: Includes the following steps: Step 1: Add cyclohexane and organic alcohol to the solid-liquid mixer in the specified proportions; Step 2: Solid alkali is added to a solid-liquid mixer and crushed and stirred using an emulsifier. After being mixed evenly, the feed flow rate is controlled by a precise metering device and continuously fed into a dynamic tube reactor. Step 3: Carbon disulfide is continuously added to the dynamic tubular reactor using a precision metering plunger pump. After the reaction is completed, the slurry enters the slurry storage tank from the outlet of the dynamic tubular reactor. Step 4: The slurry is pumped to a vacuum spray drying system by a screw pump and dried to obtain alkyl xanthate.

2. The method for continuous production of alkyl xanthates according to claim 1, characterized in that: The solid alkali is sodium hydroxide or potassium hydroxide, wherein the sodium hydroxide content is ≥96% and the potassium hydroxide content is ≥90%.

3. The method for continuous production of alkyl xanthates according to claim 1, characterized in that: The molar ratio of cyclohexane, organic alcohol, carbon disulfide, and solid alkali is 2-10:1-1.05:0.95-1.1:1-1.

1.

4. The method for continuous production of alkyl xanthates according to claim 1, characterized in that: The organic alcohol is any one or a mixture of any two or more of the following in any proportion: fatty alcohol, ethanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, n-hexanol, isohexanol, n-octanol, and isooctanol.

5. The method for continuous production of alkyl xanthates according to claim 1, characterized in that: The synthesis residence time in the dynamic tube reactor is 5-50 min, the temperature in zone one is 20-28℃, the temperature in zone two is 28-40℃, and the liquid holdup is 1-10 L.

6. The method for continuous production of alkyl xanthates according to claim 1, characterized in that: The feed rate and residence time of the dynamic tubular reactor are controlled by a feed pump.

7. The method for continuous production of alkyl xanthates according to claim 1, characterized in that: The vacuum spray drying system includes a raw material tank, a heating chamber, a separation chamber, a discharge tank, a condenser, and a water replenisher. The raw material tank is preheated to a temperature of 75-90°C, and the temperature in the heating chamber is raised to 110-140°C. The material enters the separation chamber together for solvent removal and drying. The dried product enters the product discharge tank via a screw conveyor, and the solvent is separated after condensation.

Images